There will be times when you purchase a circuit that does not appear to work no matter what you do. This is more than likely a circuit with a TTL output. (Transistor to Transistor Logic)
A case being the Infrared Sensors shown below where the output is TTL. Most sensors available at the moment are similar to the one opposite They appear to be good value for money, however they will not Trigger anything other than a logic circuit.  The circuit above will  convert the trigger signal into something that can switch on a relay.